Method and an arrangement for drying of dispersions by atomizing

ABSTRACT

A dispersion of fine material in a liquid is first concentrated in a centrifuge to a paste like consistence. It is subsequently atomized by ejecting it under centrifugal force with a high overpressure into a stream of hot gas, where it is dried and supplied together with the drying gas to a separator.

United States Patent [1 1 Putterlik June 19, 1973 METHOD AND ANARRANGEMENT FOR DRYING OF DISPERSIONS BY ATOMIZING [75] Inventor: JanPutterlik, Janackovo Nabrezi, Czechoslovakia [73] Assignee:Ceskoslovenska akademie ved,

Praha, Czechoslovakia 22 Filed: June 9,1971

21 Appl.No.:151,203

[30] Foreign Application Priority Data June 15, 1970 Czechoslovakia4163/70 [52] US. Cl. 34/8, 34/17, 34/58,

[51] Int. Cl. .Q F26b 5/08 [58] Field of Search 34/8, l7, 19, 58,

[56] References Cited UNITED STATES PATENTS 3,327,401 6/1967 Stamos etal. 34/]? X 729,009 5/1903 Sutton et al 34/57 E Primary ExaminerJohn J.Camby Attorney-Richard Low and Murray Schaffer 57] ABSTRACT A dispersionof fine material in a. liquid is first concentrated in a centrifuge to apaste like consistence. It is subsequently atomized by ejecting it undercentrifugal force with a high overpressure into a'stream of hot gas,where it is dried and supplied together with the drying gas to aseparator.

8 Claims, 2 Drawing Figures msmwmw 3.73%.481

SHEEI 2 BF 2 ML) (POW-5R1! INVENTOR METHOD AND AN ARRANGEMENT FOR DRYINGOF DISPERSIONS BY ATOMIZING BACKGROUND OF THE INVENTION This inventionrelates to a method and to apparatus for the drying of dispersions byatomizing the same, using a combination of a centrifuge and of a dryingdevice combined in a unit.

A large number of methods and of arrangements for concentratingsuspensions is known. Recently centrifuges were preferred for thispurpose, as they enable a continuous and economic operation. Thecentrifuges of course do not provide as do concentrating devices aproduct which would be entirely free of the dispersion medium used andthe material therefore has to be subsequently dried. One of the mostadvanced methods for drying suspensions is by atomizing the suspensionand a number of different arrangements have because known, which applythis method. Atomizing is preferred because it enables a dried materialto be obtained from a liquid suspension in the shape of a fine powderhaving high grade properties, and at relatively high output levels.

Atomizing drying as actually used has the drawback, however, that theprocessed suspension must be sufficiently fluid to enable it to bepumped and atomized. That means, that it must contain a relatively highcontent of liquid, which must be evaporized in the drying device. As aresult the efficiency of the whole arrangement is thus reduced. Underthese conditions the suspension cannot be mechanically concentrated to ahigh degree prior to its supply to the atomizing drying devices and thedrying process must still include a final drying step employing devicescustomary for other drying methods. As a result a final product isprovided which does not have the consistency and high grade as isnormally expected from the atomizing driers.

SUMMARY OF THE INVENTION It is an object of this invention to provide amethod and an arrangement, which greatly reduces mechanically the amountof dispersion liquid required in the dispersion prior to its supply foratomizing drying.

It is another object to increase to overall efficiency for the dryingplant of dispersions.

It is still another object of this invention to provide a process and anarrangement, which would operate continuously and with the leastrequirements for attendance.

Bearing these and other objects in mind, the present invention providesa process wherein the dispersion is first concentrated in a centrifugeto a paste like consistency and the thus concentrated dispersion isejected under a pressure generated by centrifugal force by atomizingmeans from the circumference of the centrifuge drum directly into astream of hot drying gas.

DESCRIPTION OF DRAWINGS An examplery embodiment of an arrangementoperating according to this method is shown schematically in theaccompanying drawings, where FIG. I is an axial view of a part of acentrifuge drum in cross section and FIG. 2 indicates the drying spaceprovided around the centrifuge drum.

DESCRIPTION OF PREFERRED EMBODIMENT With reference to FIG. 1 acentrifuge drum 1 rotating in the direction of the arrow 6 is providedon its circumference with jets 3. By means of the jets 3 theconcentrated suspension is in the course of rotation of the centrifugedrum 1 either periodically, continuously, or in dependence on the amountof the concentrate col lected around the jet 3 injected at high pressureinto the substantially annular space 4 at the circumference of thecentrifuge drum 1 limited by the stator shell 5. Hot air or some otherhot gas isintroduced by way of a supply tube 8 into the space 4. Acorrect and efficient operation of the whole unit supposes, that only afraction concentrated to a predetermined high degree is injected atsubstantial overpressure over the jets 3 into space 4. A similarcentrifuge is used where the jets releasing the concentrated suspensionare only opened, if a certain amount of concentrate has collected in theneighborhood of the jet and are closed again if most of this concentratehas been ejected. As the centrifuge drum 1 rotates at high speed and itscircumferential speed is equally high the material ejected by the jets 3is atomized upon leaving the jets 3 and forms a mist which with theincreased surface of the atomized particles, is instantaneously dried.The method according to this invention has with respect to actually usedmethods the advantage, that due to a previous high concentration in thecentrifuge a substantially smaller amount of liquid has to beevaporated. It requires therefore rather less heat energy, maintainingall other advantages, particularly a dry andpowderous product obtainedby a single stage process. The described method enables the creation ofa complex aggregate comprising a concentrating centrifuge actingsimultaneously as atomizing device an a drying unit comprising a heatsource, a circulating system and a separator of the dried material. Thedrying unit can be arranged differently to meet different requirementsof the used material. The gas stream in the annular space 4 can besupplied for'instance in the same direction as the rotation of thecentrifugedrum l or in counter-current, or the gas can be introduced inthe axial direction of the centrifuge drum, or if desired in mutuallyopposite directions.

An exemplary embodiment is indicated in FIG. 2. It shows schematically acentrifuge drum 1, provided at its circumference with radial blades 13.The concentrate is ejected by not shown jets 3 of the centrifuge drum 1(see also FIG. 1) in direction of arrows 7 into the annular space 4determined by the stator shell 5. The stator shell 5 has a supply tube 8for the supply of the drying gas in direction of the arrow 9 and atangentially attached discharge tube 10 for discharging the used hot gaswith the dried material in direction of the arrow 11 to a separator ofthe dried material. The supply tube 8 terminates with its narrowedextremity 12 into the stator shell in direction of the arrow 9, at theangle a with respect to the centripetal direction.

The whole arrangement operates as follows: by a suitable selection ofthe angle a and by the action of the blades 13 of the centrifuge drum 1a quick movement of the drying gas in direction of the arrows 14 isachieved in the annular space 4 of the stator shell 5. The concentratedmaterial is injected in direction of arrows 7 from the centrifuge druminto this stream of drying gas and as it is atomized to mist and itssurface increased, it is instantaneously dried. The mixture of dryinggas which has taken over the liquid fraction and the dried loosematerial are discharged via the discharge tube in direction of thearrowll to a not shown separator of the dried solid material. It isadvantageous, if the stator shell 5 is additionally heated, for instanceby means of an electric resistance wire 15. Thus even in case of someinstantaneous overloading of the drying device or in case of somereduction of the efficiency of the drying device, that is in case ofsome accidental failure, no sticking of the dried material on the wallsof the stator shell 5 is experienced.

The complex solution of concentration and drying to a single aggregateaccording to this invention represents a fully automized arrangement forconcentration of fine dispersions up to a dry state.

I claim:

1. A method for drying fine material dispersed in a liquid comprisingthe steps of supplying said dispersion to a centrifuge, rotating saidcentrifuge at a speed sufficient to concentrate said dispersion into apaste like consistency, atomizing said concentrated paste and ejectingsaid atomized paste from said centrifuge under pressure into an annularpath, and supplying heat to said atomized paste in said annular pathuntil said material in said atomized paste is dried.

2. The method according to claim 1 including the step of introducing astream of heated gas into said annular path in contact with saidatomized paste.

3. The method according to claim 1 wherein the ejection and atomizing ofsaid concentrated paste is effected as a result of the centrifugalaction of said centrifuge.

4. Apparatus for drying dispersions of fine material 4 in a liquidcomprising:

a centrifuge having a rotating centrifuge drum, adapted to concentratesaid dispersion into paste like consistency,

a plurality ofjets at the circumference of said centrifuge drum adaptedto atomize the concentrated dispersion,

a stator shell surrounding said centrifuge, and defining a substantiallyannular space around the circumference of the centrifuge drum into whichsaid atomized concentrated dispersion is received,

a supply tube for delivering hot gas terminating into said annular spaceto dry said atomized concentrated dispersion, and

a discharge tube for the discharge of the mixture of dried material andof said gas from said annular space.

5. The apparatus as set forth in claim 4, wherein said centrifuge drumis provided on its circumference with a number of blades adapted topromote the rotating movement of the drying gas in said annular spacearound the circumference of the centrifuge drum.

6. The apparatus as set forth in claim 4, wherein the stator shell isprovided with means for additional heating.

7. The apparatus as set forth in claim 4, wherein said discharge tube isconnected to said shell to extend tangentially therefrom.

8. The apparatus as set forth in claim 4, wherein said supply tube has anarrow constricting portion terminating at said annular space.

* III

1. A method for drying fine material dispersed in a liquid comprisingthe steps of supplying said dispersion to a centrifuge, rotating saidcentrifuge at a speed sufficient to concentrate said dispersion into apaste like consistency, atomizing said concentrated paste and ejectingsaid atomized paste from said centrifuge under pressure into an annularpath, and supplying heat to said atomized paste in said annular pathuntil said material in said atomized paste is dried.
 2. The methodaccording to claim 1 including the step of introducing a stream ofheated gas into said annular path in contact with said atomized paste.3. The method according to claim 1 wherein the ejection and atomizing ofsaid concentrated paste is effected as a result of the centrifugalaction of said centrifuge.
 4. Apparatus for drying dispersions of finematerial in a liquid comprising: a centrifuge having a rotatingcentrifuge drum, adapted to concentrate said dispersion into paste likeconsistency, a plurality of jets at the circumference of said centrifugedrum adapted to atomize the concentrated dispersion, a stator shellsurrounding said centrifuge, and defining a substantially annular spacearound the circumference of the centrifuge drum into which said atomizedconcentrated dispersion is received, a supply tube for delivering hotgas terminating into said annular space to dry said atomizedconcentrated dispersion, and a discharge tube for the discharge of themixture of dried material and of said gas from said annular space. 5.The apparatus as set forth in claim 4, wherein said centrifuge drum isprovided on its circumference with a number of blades adapted to promotethe rotating movement of the drying gas in said annular space around thecircumference of the centrifuge drum.
 6. The apparatus as set forth inclaim 4, wherein the stator shell is provided with means for additionalheating.
 7. The apparatus as set forth in claim 4, wherein saiddischarge tube is connected to said shell to extend tangentiallytherefrom.
 8. The apparatus as set forth in claim 4, wherein said supplytube has a narrow constricting portion terminating at said annularspace.